The present invention relates to a process for the treatment of laundry in a washing machine, more particularly of the type in which the laundry is sprinkled with a washing liquid and also relates to a washer which operates on the basis of such a method.
At present, conventional laundry washing machines comprise a collector mounted beneath the wash tub and in fluid communication therewith for receiving the washing liquid from the wash tub, an electric recirculation pump connected to the collector and to an upper portion of the tub, the electric pump being operable to bring about a repeated recirculation of the washing liquid passed through the tub and into the collector and back to the tub by sprinkling or rinsing the liquid onto the laundry contained in a basket mounted in the tub.
More particularly, U.S. patent application Ser. No. 677,302, filed Dec. 3, 1984 (now U.S. Pat. No. 4,580,421) discloses a laundry washing machine which includes a washing tub, a laundry containing drum and a collector for the washing liquid which is positioned beneath and connected to the washing tub, the collector being so shaped as to contain at least a filtering element, an electric heating element and a thermostatic sensor for respectively filtering, heating and sensing the temperature of the washing liquid.
The washing liquid collector is connected both with outlet piping of the washing machine through a usual drain pipe, and with the wash tub through a further piping system and an electric circulating pump, which can be either separate from or on the same axis with the drain pump, the electric circulating pump being provided with a suction opening connected with the wash liquid collector as well as a delivery opening connected with the further piping system.
Such a machine performs both "intensive" and "delicate" washing programs of a traditional type for washing heavily soiled clothes at normal levels of wash liquid in the tub, while keeping the circulating pump switched off for the entire duration of such washing programs, as well as "intensive" washing programs for laundering not so heavily soiled clothes at lower levels of the washing liquid in the tub and switching on the circulating pump during certain periods during such washing programs in such a way that the washing liquid is repeatedly circulated from the collector into the tub through the piping system and is directly sprayed onto the clothes.
In particular, these special "intensive" washing programs are used to wash not so heavily soiled cottons and/or heat-resistant synthetics by filling the washing liquid into the collector at different reduced levels according to the actual wash load in the drum. The "intensive" washing programs are carried out by heating the washing liquid at predetermined temperatures with values up to no more than about 90.degree. C., turning on the heating element, and thermostatic control of the heating element is carried out by the thermostatic sensor. This type of washing machine has proven to be satisfactory and reliable during operation and is advantageously set up for connection to a water supply system in order not to fill the tub with the desired quantity of water, together with detergents, to thereby insure the proper development of the washing programs described above.
However, this washer has drawbacks when the element for heating the washing liquid must be eliminated, such as when regulations do not permit the use of such heating elements. In such cases, the washer must therefore be connected to preexisting centralized plants in which the water of the water supply system is preheated by suitable water heaters or similar devices.
Under such conditions, the water is heated at relatively elevated temperatures on the order of about 60.degree. C. but the water is partially cooled upon coming into contact with the laundry, the metal parts of the basket, and with the wash tub, all of which are at temperatures lower than that of the incoming water. As a result, the water introduced into the tub is cooled to a temperature lower than that required and the washing programs for the washer in which the water is recirculated cannot be carried out satisfactorily.